Question

我是XML解析商务的新手。很抱歉愚蠢的问题。

我想浏览我的XML：

<?xml version="1.0"?>
<catalog>
   <book id="bk101">
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
      <genre>Computer</genre>
      <price>44.95</price>
      <publish_date>2000-10-01</publish_date>
      <description>An in-depth look at creating applications 
      with XML.</description>
   </book>
   <book id="bk102">
      <author>Ralls, Kim</author>
      <title>Midnight Rain</title>
      <genre>Fantasy</genre>
      <price>5.95</price>
      <publish_date>2000-12-16</publish_date>
      <description>A former architect battles corporate zombies, 
      an evil sorceress, and her own childhood to become queen 
      of the world.</description>
   </book>
   <book id="bk103">
      <author>Corets, Eva</author>
      <title>Maeve Ascendant</title>
      <genre>Fantasy</genre>
      <price>5.95</price>
      <publish_date>2000-11-17</publish_date>
      <description>After the collapse of a nanotechnology 
      society in England, the young survivors lay the 
      foundation for a new society.</description>
   </book>
   <book id="bk104">
      <author>Corets, Eva</author>
      <title>Oberon's Legacy</title>
      <genre>Fantasy</genre>
      <price>5.95</price>
      <publish_date>2001-03-10</publish_date>
      <description>In post-apocalypse England, the mysterious 
      agent known only as Oberon helps to create a new life 
      for the inhabitants of London. Sequel to Maeve 
      Ascendant.</description>
   </book>
   <book id="bk105">
      <author>Corets, Eva</author>
      <title>The Sundered Grail</title>
      <genre>Fantasy</genre>
      <price>5.95</price>
      <publish_date>2001-09-10</publish_date>
      <description>The two daughters of Maeve, half-sisters, 
      battle one another for control of England. Sequel to 
      Oberon's Legacy.</description>
   </book>
   <book id="bk106">
      <author>Randall, Cynthia</author>
      <title>Lover Birds</title>
      <genre>Romance</genre>
      <price>4.95</price>
      <publish_date>2000-09-02</publish_date>
      <description>When Carla meets Paul at an ornithology 
      conference, tempers fly as feathers get ruffled.</description>
   </book>
   <book id="bk107">
      <author>Thurman, Paula</author>
      <title>Splish Splash</title>
      <genre>Romance</genre>
      <price>4.95</price>
      <publish_date>2000-11-02</publish_date>
      <description>A deep sea diver finds true love twenty 
      thousand leagues beneath the sea.</description>
   </book>
   <book id="bk108">
      <author>Knorr, Stefan</author>
      <title>Creepy Crawlies</title>
      <genre>Horror</genre>
      <price>4.95</price>
      <publish_date>2000-12-06</publish_date>
      <description>An anthology of horror stories about roaches,
      centipedes, scorpions  and other insects.</description>
   </book>
</catalog>

而我试图运行的代码（遵循互联网教程）是：

tinyxml2::XMLDocument mappedxml1;
XMLError eResult = mappedxml1.LoadFile(filename1);
if(eResult == XML_SUCCESS){
        printf("XMLERROR is %d\nXML loading successfull.\n",eResult);
    }
    else{
        printf("XMLERROR is %d\nXML loading unsuccessfull.\n",eResult);
    }
XMLNode * pRoot1 = mappedxml1.FirstChild();
    if(pRoot1 == NULL){printf("ERROR: NO ROOT\n");}
    else{printf("Good pointer\n");}
XMLElement * pbook1 = pRoot1->FirstChildElement("book id");
    if (pbook1 == NULL){printf("ERROR PARSING ELEMENT\n");}
    else{printf("GOT IT\n");}

虽然pRoot1很合适，但pbook1的值始终为NULL。我希望它指向bk101

任何帮助或建议？提前谢谢你

Answer 1

您正在尝试查找名为book id的元素。没有这样的元素。

但是，有一些名称为book的元素！（每个人都有一个名为id的属性。）

您还需要解析器跳过您的XML声明，目前正被FirstChild调用捕获（因此*pRoot1不是你认为它是什么！）。您可以尝试使用FirstChildElement("catalog")。

顺便说一句，我建议您查看错误处理程序;此时，如果pRoot1是一个空指针，那么你向控制台写一条消息，然后愉快地继续尝试解除引用该空指针。

为什么我在C ++中使用tinyXML2获得NULL指针？

1 个答案: